Compound bows inherently suffer from cam lean as a result of a number of factors such as side loads produced by cable guards, inconsistency of limbs, and varying loads on different tracks of cams. Cam lean is a disadvantage to the archer because of the possibility of strings derailing from their tracks during use. Also, excessive lean will tend to prematurely cause string failure and cable wear. The present invention incorporates dual limbs and independent dual limb adjustments which lead to the ability to control wheel lean and minimize string and cable wear. The independent dual limb adjustment has two separate limb containment devices. There is a means for adjusting the limbs independently, and it may be possible to modify to adjust both limbs in unison. The adjustment will either increase or decrease the draw weight of the bow. Also. if one of the limbs is adjusted independently of the other, it will cause the cam to lean one way or the other. The cams can thus be adjusted to provide the strings with a straight path to follow in their respective grooves. Further, the dual limbs permit the mounting of the axle for the cam to be positioned closer to the riser, thus enabling the utilization of shorter limbs and larger cams.
The limbs are also mounted for a variable limb angle so that not only may the tension or draw weight of the bow be changed, but the actual limb geometry may be changed. That is, it is possible to have the same limb tension but different limb positions. Changing the limb angle will change the geometry of the bow and will change the axle-to-axle length. This adjustable limb angle is not accomplished with the usual limb bolt (that is still provided to adjust draw weight) but by multiple fixed positions determined by the mounting holes in the riser and a positioning pin for securing the limb pockets in a predetermined angular position with respect to the riser. Modifying the bow geometry by positioning the limbs at a greater angle with respect to the riser gives the bow a better feel to the archer. Further, this positioning of the limbs raises the brace height and gives the bow better performance, usually in the form of a smoother launch of an arrow. Importantly, the archer has the ability to completely change the bow by adjusting the pockets, changing strings and cable, and still have the bow exhibit the same peak weight and draw length. This versatility is provided without the utilization of professional help and special equipment such as a bow press.
An important feature is the fact that the limbs can be positioned such that when the bowstring is at full draw, the axle of the respective cam or wheel is drawn toward the center of the riser, and may be drawn beyond parallel with respect to each other or beyond a horizontal reference line drawn from the respective axle to corresponding pivot point of each limb. When this geometry is chosen, the release of the bowstring will result in the arcuate travel of the axle of the wheel and cam that initially has a significant component of reaction force that is directed forward, or away from the archer. This initial force results in a smoother release; the initial reaction of the bow resulting from the release is less noticeable to the archer as with previous bow configurations. The stored energy expended during the release is now more balanced and is directed up and down as the axles of the cam and wheel first travel rearward toward the archer and then upward as the arcuate travel of the axles pass through horizontal and end with forward travel at the end of the release. Thus, the “feel” of the reaction force as detected by the archer during release is smoother and with a lower amplitude.
The utilization of independent dual limbs avoids limb fatigue and possible failure as a result of twisting moments caused by large cam profiles with strings or cables entering or exiting their respective tracks out of the plane of the cam. The independent dual limbs are each independently adjustable to accommodate such uneven forces.
The utilization of a ratio of approximately 0.22 or less limb length (measured from limb pivot to axis of the cam/wheel axle) to riser length (measured from limb pivot to limb pivot) provides several manufacturing advantages. The riser can be manufactured from bar stock instead of an expensive extrusion because the length of an extrusion to provide the above ratio would be extremely expensive. Further, the riser length accepts shorter limbs that can be angled with respect to the riser to provide a high brace height. The low ratio provides for longer risers and shorter limbs that may be angled backwardly toward the archer and permit the mounting of cams/wheels such that at full draw, the axles of the cam/wheel follow an arcuate path to positions where the respective limbs are parallel and ultimately beyond parallel. Upon release, the axles and the respective wheel/cam travel rearward toward the archer to provide an initial reaction force opposite to that experienced with conventional riser limb cam axle configurations.